Lord David Puttnam is one of the key players in the future of Channel 4. The broadcaster's deputy chairman, he is one of its staunchest defenders but he has also been a fierce critic, particularly over its handling of the Celebrity Big Brother race row.

With the prospect of privatisation looming once again and the station's public service track record under greater scrutiny than it has been for years, Channel 4 needs people like Lord Puttnam to fight its corner.

Calling for an update of Channel 4's remit, he said it was no good the channel being challenging and controversial if it was not also "respected and trusted".

"We're now dealing with programme makers of a different generation," he told Media Talk, the MediaGuardian podcast. "The way they see themselves regarded by their peer group is in terms of how controversial they could be." Who could he possibly be talking about?

Lord Puttnam is the BBC chairman who might have been. A front-runner to chair the newly created BBC Trust, he ruled himself out after a month of agonising saying he could not commit to the four-days-a-week post.

Perhaps he will one day end up being chairman of Channel 4 instead.

Chairman of the parliamentary committee that examined the 2003 Communications Act, Lord Puttnam led the campaign to insert the so-called "Murdoch clause" on cross-media ownership.

A vocal opponent of BSkyB's purchase of a 17.9% stake in ITV, Lord Puttnam said it "should not be allowed to stand", and called on politicians to question "any further extension of [Rupert] Murdoch's tentacles".

He claimed there was a "conspiracy of silence ... fuelled by a fear of alienating the most powerful media owner in the country".

He was also critical of the BBC's decision to close its online learning site, BBC Jam. He said the BBC Trust, barely three months into its existence, was watering down the public service purposes that it was set up to protect.

And he hit out at the "sometimes offensive" salaries the BBC pays to stars such as Jonathan Ross.

"As an institution it is far from perfect," he wrote. "But it does continue to offer the possibility of an eventual victory for sanity over nihilism in the evolution of the nation's media output."

One of a generation of former advertising executives who helped rejuventate the British film industry three decades ago, Lord Puttnam produced Chariots of Fire, Bugsy Malone and The Killing Fields. He became the only non-American to run a Hollywood film studio during an unhappy two-year stint in charge of Columbia Pictures.

As well as his role at Channel 4, Lord Puttnam is also president of Unicef, chair of the Teaching Awards Trust, and chancellor of Sunderland University. He returned to his roots in advertising earlier this year when he became chairman of Profero.

· To contact the MediaGuardian newsdesk email editor@mediatheguardian.com or phone 020 7239 9857. For all other inquiries please call the main Guardian switchboard on 020 7278 2332.

· If you are writing a comment for publication, please mark clearly "for publication".